Fluid actuated impact mechanism

ABSTRACT

PLIED TO THE CHAMBER THROUGH A ROTARY VALVE FORMED BY THE DRIVE MEMBER AND A PORTION OF A ROTARY ANVIL FOR FORCING THE HAMMER TO MOVE AXIALLY AND ACCELERATE ROTATIVELY TO IMPART THE ANVIL.   A ROTARY FLUID ACTUATED MECHANISM FOR AN IMPACT WRENCH INCLUDING A ROTARY DRIVE MEMBER COUPLED TO A ROTATING HAMMER MEMBER THROUGH A PIN AND SLOT COUPLING WHICH PROVIDES FOR ROTARY AND AXIAL DISPLACEMENT OF THE HAMMER WITH RESPECT TO THE DRIVE MEMBER, THE HAMMER IS MOUNTED IN SLEEVED ARRANGEMENT OVER THE DRIVE MEMBER TO FORM AN EXPANSIBLE CHAMBER. PRESSURE AIR IS SUP-

Feb. 6, 1973 ZOERNER ET AL 3,714,994

FLUID ACTUA'IEI) .I'MlAC'I MECHANISM Filed Nov. 29, 1971 3 Sheets-Sheet1 Feb. 6, 1973 ZQERNER ET AL 3,714,994

FLUID ACTUATED IMPACT MECHANISM Filed Nov. 29, 1971 3 3 Sheets-Sheet 297 64 x50 A 60 I A, 74 58 x 2.; 6.2 F K M; S g 82 f,

fig 4 Feb. 6, 1973 R. 1... ZOERNER ET AL 3,714,994

FLUID ACTUATED IMPACT MECHANISM Filed Nov. 29, 1971 I5 Sheets-Sheet 3 I@J fi s 1F? g TI United States Patent Oflice 3,714,994 Patented Feb. 6,1973 3,714,994 FLUID ACTUATED IMPACT MECHANISM Richard L. Zoerner,Marne, and Larry D. Ruiter, Grand Haven, Mich., assignors toGardner-Denver Company, Quincy, Ill.

Filed Nov. 29, 1971, Ser. No. 202,925 Int. Cl. B2511 15/00 US. Cl.173-93 9 Claims ABSTRACT OF THE DISCLOSURE A rotary fluid actuatedmechanism for an impact wrench including a rotary drive member coupledto a rotating hammer member through a pin and slot coupling whichprovides for rotary and axial displacement of the hammer with respect tothe drive member. The hammer is mounted in sleeved arrangement over thedrive member to form an expansible chamber. Pressure air is supplied tothe chamber through a rotary valve formed by the drive member and aportion of a rotary anvil for forcing the hammer to move axially andaccelerate rotatively to impact the anvil.

BACKGROUND OF THE INVENTION Impact wrench mechanisms are known in whichpressure air is admitted to an expansible chamber to force a rotatinghammer axially into a position wherein further rotation will result inimpacting of the hammer against an anvil. U.S. Pats. 3,068,973 to S. B.Maurer and 3,104,- 743 to H. C. Reynolds disclose impact mechanisms ofthe general type above mentioned. However, known types of fluid actuatedmechanisms for impact wrenches do not provide for rotary acceleration ofthe hammer with respect to the motor rotor to provide for impacting theanvil with greater kinetic energy than that which is provided by therotary motor. Accordingly, the motive air expended to axially move thehammer into anvil impacting position is not put to any other usefulpurpose and is merely exhausted to permit the hammer to retract prior toanother impacting cycle. Moreover, known types of impact wrenchmechanisms which use pressure air to axially move the hammer into anvilimpacting position use pressure air to retract the hammer, which isineflicient, or mechanical springs which are subject to breakage andcontributes to the complexity of the impact mechanism.

SUMMARY OF THE INVENTION The present invention provides an impactdelivery mechanism which is actuated by pressure fluid to causeimpacting engagement of a rotating hammer with an anvil and whichincludes a drive coupling between the hammer and a rotary drive memberwhich is operable to retract the hammer out of anvil impacting position.The improved impact delivery mechanism of the present invention providesa drive coupling between a drive member and a rotary impact hammer whichis operable to rotatably accelerate the hammer to a rotary speed greaterthan the rotary speed of the drive member in response to pressure fluidbeing applied to'axially move the hammer into anvil engaging position.In accordance with the present invention an impact wrench mechanism isprovided which uses pressure fluid more efliciently than known pressurefluid actuated impact wrench mechanisms.

The present invention further provides an impact delivery mechanismwhich includes valve means for supplying a sufficient quantity ofpressure fluid to axially and rotatably move a hammer element to impactan anvil and for rapidly exhausting said quantity of pressure fluid toreduce delay in hammer retraction movement. The arrangement of therotary valve together with the drive coupling between the hammer memberand the drive member also prevents the hammer from striking a secondaryim pact blow during the operating cycle. With the present invention anyrebound action of the hammer assists the hammer retraction movement andis also dissipated through pumping residual air from an expansiblechamber formed between the hammer and drive member instead of beingtransmitted as a reaction force acting through the tool motor to thetool operator. Significantly, the present invention also provides animpact delivery mechanism which includes relatively few working partsand is reliable and economical to manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal section viewtaken along the centerline of an impact wrench including the impactdelivery mechanism of the present invention;

FIGS. 2, 4, 6 and 8 are detail views showing the relative positions ofthe hammer member, drive member, and anvil during a portion of anoperating cycle of the impact mechanism of FIG. 1;

FIGS. 3, 5, 7, and 9 are section views taken substantially along theline 33 of FIG. 2 and showing the relative positions of the drivemember, and anvil in the respective FIGS. 2, 4, 6, and 8, and alsoshowing, with broken lines superimposed on the views, the relativepositions of the dogs on the hammer and anvil;

FIG. 10 is a view taken substantially along a line in the same locationas line 3-3 showing an alternate embodiment of the anvil providing fortwo impact blows per revolution of the drive member;

FIG. 11 is a section taken substantially along the line 1111 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 11 afluid operated impact wrench is illustrated and generally designated bythe numeral 10. The wrench 10 is characterized by a housing 12 having ahand grip portion 14. A rotary vane fluid motor 16, disposed within thehousing 12, includes a rotor 18. The motor 16 is of a type generallywell known and extensively used in fluid operated power tools. Pressurefluid is supplied to the motor 16 through a passage 20 in which isinterposed a fluid flow control valve 22 of conventional construction.The valve 22 is spring biased in the closed position and is operable tobe opened by actuation of a trigger 24 to provide flow of fluid such ascompressed air to the motor 16. The wrench 10 also includes a motorreversing valve generally designated by the numeral 26 and being of atype generally well known. The valve 26 is operated by a lever 28 to bepositioned to provide for flow of fluid to spaced apart motor inletports, not shown, for reversible operation of the motor 16. The wrench10 also includes a housing portion 32 removably secured on the housing12 by a retaining ring 34 which is clamped to the housing 12 by suitablefasteners, not shown. The housing portion 32 contains, within itsinterior, an improved impact mechanism generally designated by thenumeral 33 and described further herein.

The motor rotor 18 extends through a bearing 35 into the interior of thehousing portion 32 and is drivably connected to a rotatable drive member36 by interengaging splines 38 located on the rotor and the drivemember. The drive member 36 has a cylindrical exterior surface 40 and acylindrical recess 42 opening to one end. The drive member 36 alsoincludes a central bore 44 in which a reduced diameter portion. 46 ofthe rotor shaft is located and sealingly surrounded by an O-ring 48.

The drive member 36 supports a substantially cylindrical member 50comprising the hammer of the impact mechanism 33. The hammer member 50includes a cylindrical inner wall 52 which is proportioned to be inclose fitting relationship to the surface 40. The hammer member 50 is,however, disposed for limited axial and rotatable movement relative tothe drive member 36. The hammer member 50 also forms, together with thedrive member 36, an expansible chamber 54 into which pressure fluid maybe admitted to act on a pressure surface 56 for axially and rotatablymoving the hammer with respect to the drive member as will be explainedherein. Projecting axially from one end of the hammer member are twohammer dogs 58 integrally formed on the hammer and radially disposed 180apart.

As shown in FIGS. 2, 4, 6, 8, and 11 the hammer member 50 and drivemember 36 are interconnected by a drive coupling comprising a projectionformed by a cylindrical pin 60 suitably retained on the drive member 36and projecting radially from the surface 40. The pin 60 is disposed in asubstantially triangular shaped slot 62 formed on the hammer member 50and having two axially converging surfaces 64 and 66. The corners of thetriangular shaped slot 62 are formed by radii which are dimensionallyslightly larger than one-half of the diameter of the cylindrical pin 60.A suitable angle subtended by the surfaces 64 and 66 is in the range of90 to 100.

The impact mechanism 33 also includes an anvil 68 rotatably supported ina bearing 70 located in the housing portion 32. The anvil 68 includes adrive end portion 72 of conventional configuration for suitably mountinga wrench socket or the like thereon. A pair of radially extending dogs74 are also formed on the anvil 68 and comprise means operable toreceive impact blows from the cooperating dogs 58 on the hammer member50 in a manner Well known.

The opposite end of the anvil is formed as a circular shaft portion 76which extends in close fitting and substantially fluid sealingrelationship through an opening 78 in the hammer member 50 and into abore 80 in the drive member 36. The shaft portion 76 has an axialpassage 82 in communication with a radial passage 84 and with an axialpassage 86 formed entirely through the rotor 18. The passage 86 is incommunication with the passage by way of a passage 87.

The anvil also includes a groove 88 formed on the periphery of the shaftportion 76 and operable, as shown in FIG. 1 and FIG. 5, to be incommunication with a passage 90 and a passage 92 in the drive member 36.The passage 90 is formed as a radial slot and opens into the expansiblechamber 54. The passage 92, which together With the groove 88 forms anexhaust passage, opens into the interior of the housing portion 32. Anopening 94 in the housing portion 32 conducts pressure fluid to apassage 96 which forms part of an exhaust port for the motor 16. Thepassages 90 and 92 in the drive member 36 cooperate with the groove 88and passage 84 in the anvil 68 to form rotary valve means for admittingpressure fluid to and exhausting pressure fluid from the expansiblechamber 54. The operation of the rotary valve means may be betterunderstood from a description of an operating cycle of the impactmechanism 33.

With pressure fluid supplied to the wrench 10, the valve .22 open, andthe reversing valve 26 set to rotate the motor 16 so that the hammermember 50 is rotated in the direction indicated by the arrows in FIGS. 2and 3, the drive pin 60 will be located in the slot 62 in the positionshown in FIG. 2. In this condition the expansible chamber 54 isexhausted of pressure fluid and the hammer member 50 is axiallyretracted such that the dogs 58 will not be in an axial position toengage the dogs 74. As shown in FIG. 3 the passage 90 is not incommunication with the groove 88 or the passage 84. It is assumed thatthe anvil 68 is not moving due to suflicient resistance to rotation of afastener, not shown, which is to be tightened or removed by the wrench10. As the drive member 36 and hammer member 50 continue to rotate tothe position shown in FIGS. 4 and 5 the passage 84 is now in fullregistration with the passage 90 to communicate pressure fluid to theexpansible chamber 54. Pressure fluid acting on the surface 56 alreadyhas moved the hammer member 50 axially toward the anvil 68 and at thesame time the hammer is forced to accelerate rotatably with respect tothe drive member 36 due to the engagement of the pin 60 with the axiallysloping surface '64. As pressure fluid is admitted to the chamber 54 thehammer member 50 moves from the position of FIGS. 4 and 5 to theposition shown in FIGS. 6 and 7. In moving from the BIG. 2 to the FIG. 6position, the hammer member 50 has moved axially with respect to theanvil so that the dogs 58 will be in a proper axial position forengaging the dogs 74 on the anvil. The hammer member 50 has alsoaccelerated rotatably with respect to the drive member 36 so that thetotal rotational kinetic energy of the hammer member is greater than theamount of rotational kinetic energy in the hammer member due to therotational speed of the drive member alone. Accordingly, the impact blowdelivered to the anvil 68 is increased and the pressure fluid expendedto move the hammer member is used more efficiently than in prior artimpact mechanisms.

A number of factors such as motor size, working air pressure, moment ofinertia of the motor and hammer, and positional relationships betweenthe cooperating hammer and anvil dogs and the rotary valve arrangementare important to providing a desired improved impact wrench inaccordance with the present invention. By way of example it has beendetermined that an improved wrench sized for driving one-half inchthread diameter fasteners may use a conventional six-bladed rotary vaneair motor of approximately 1.4 inch rotor diameter by 1.4 inch rotorlength. The combined mass moment of inertia of the motor rotor 18 anddrive member 36 with respect to the rotor axis has been determined to beabout .00072 pounds-inches-seconds 2 and the mass moment of inertia ofthe hammer 50 about .0012 pounds-inches-seconds The rotational angulardisplacement of the hammer 50 with respect to the member 36 provided bythe drive pin 60 and sloping surface 64 is about 20. Together with theaforementioned conditions the desired angular displacement between thecooperating impact surfaces on the dogs 58 and 74 has been found to bein the range of to 95 at the instant that the passage commences toregister with the passage 84. Assuming adequate passage area to preventthrottling of air flowing to the chamber 54, and supply pressure of70-90 p.s.i.g., the above timing relationships have been selected toprovide for the corner 97 of the slot formed by the converging surfaces64 and 66 to be not quite engaged with the pin 60 at the instant ofimpact of the dogs 58 with the anvil dogs 74. This is the position ofFIGS. 6 and 7 and as may be seen in FIG. 7 at the instant of impact thepassage 90 is at the threshold of being in registration with the groove88. As the passage 90 and groove 88 come into registration pressurefluid in the chamber 54 is we hausted through the passage 90, groove 88,and passage 92 to the interior of the housing portion 32, and eventuallythrough passage 94 to the wrench exterior. After the instant of impact,the drive member 36 continues to rotate from the position of FIGS. 6 and7 to the position of FIGS. 8 and 9 wherein the passage 90 is shown infull registration with the groove 88. With the chamber 54 relieved offluid pressure, rotation of the drive member 36 t0- gether with theresistance to rotation of the anvil 68 and rebound action of the hammer50 will cause the hammer to be cammed axially away from the anvil dogs74 as the surface 64 rides along the pin 60. The hammer member 50 anddrive member 36 will continue to rotate together from the position ofFIG. 8 to the position of FIG. 2 where the impact cycle will commenceagain. With the configuration of FIG. 1 the impact mechanism 33 willdeliver one impact blow per revolution of the drive member 36.

The cycle depicted by FIGS. 2 through 9 shows the anvil 68 in a fixedposition for clarity. The anvil will, of course, rotate an incrementalamount with each impact blow until the resistance to rotation cannot beovercome by the impact blows of the hammer member 50. The return of thehammer member from the FIG. 6 to FIG. 8 position will be cushioned bythe pumping of pressure fluid from the chamber 54. Moreover, it isbelieved the drive coupling formed by the pin 60 and slot 62 providesfor minimum or negligible stalling of the drive member 36 and motorrotor 18 upon impact, and also smooth acceleration of the motor prior todelivery of the next impact blow.

FIG. 10 illustrates a modified embodiment of the anvil shaft portion 76designated by the numeral 100. The modified shaft portion 100 includes atransverse passage 102 which is in communication with a passage 104, thelatter corresponding to the passage 82 in the embodiment of FIG. 1. .Asshown in FIG. 10 the passage 102 opens to the periphery of the shaftportion 100 at two positions 180 apart. The shaft portion 100 alsoincludes grooves 106 and 108 formed on its periphery. The grooves 106and 108 operate to communicate the passage 90 with the passage 92 in thedrive member 36 for exhausting pressure fluid from the chamber 54. Theembodiment of FIG. 10 is functionally similar to the embodiment of FIG.1 with the exception that the embodiment of FIG. 10 provides for twoimpact blows of the hammer against the anvil per revolution of the drivemember 36 as will be readily understandable to those of ordinary skillin the art of impact mechanisms. As will also be appreciated by thoseskilled in the art, the impact delivery mechanism shown in FIGS. 1through 11 is operable to deliver impact blows in both directions ofrotation of the motor rotor 18. The operation of the wrench in thedirection of rotation opposite to that shown in FIGS. 2 through 9 issubstantially the same except that the surface 66 of the slot 62cooperates with the pin 60 to provide the combined axial and rotationalmovement of the hammer member 50 with respect to the drive member 36.

What is claimed is:

1. A fluid operated impact wrench comprising:

a fluid operated motor including a rotor;

a rotatable anvil having means for receiving impact blows, and theimprovement characterized by:

a drive member operably connected to said rotor to be rotatably drivenby said rotor;

a hammer member operable to be rotatably driven by said drive member fordelivering impact blows to said anvil;

means including said hammer member defining an expansible chamber;

means for admitting pressure fluid to said expansible chamber; and,

a drive coupling interconnecting said hammer member and said drivemember for providing rotational acceleration of said hammer member withrespect to said drive member in response to the admission of pressurefluid to said expansible chamber.

2. The invention set forth in claim 1 wherein:

said hammer member is axially movable with respect to said drive memberfrom a retracted position to a position for delivering an impact blow tosaid anvil in response to the admission of pressure fluid to saidexpansible chamber.

3. The invention set forth in claim 2 wherein:

said drive coupling is operable to move said hammer member axially fromsaid position for delivering an impact blow to said retracted positionin response to the delivery of an impact blow to said anvil.

4. The invention set forth in claim 3 wherein:

said expansible chamber is formed by said hammer member and said drivemember and said hammer member includes a pressure surface defining amovable wall portion of said expansible chamber responsive to theadmission of pressure fluid to said expansible chamber to move saidhammer member axially and rotatably with respect to said drive memher.

5. The invention set forth in claim 1 wherein:

said means for admitting pressure fluid to said expansible chamberincludes rotary valve means defined by a portion of said anvilcooperable with said drive member.

6. The invention set forth in claim 5 wherein:

said rotary valve means comprises a shaft portion of said anvildisposed'in a longitudinal bore in said drive member, passage means insaid shaft portion opening radially to the periphery of said shaftportion, and passage means in said drive member opening into saidexpansible chamber and said longitudinal bore and operable to registerwith said passage means in said shaft portion in response to rotation ofsaid drive member with respect to said anvil.

7. The invention set forth in claim 6 wherein:

said anvil includes a groove disposed on the periphery of said shaftportion, said drive member includes exhaust passage means, and inresponse to rotation of said drive member with respect to said anvilsaid groove is operable to register with said passage means in saiddrive member and said exhaust passage means in said drive member toexhaust pressure fluid from said expansible chamber.

8. The invention set forth in claim 2 wherein:

said drive coupling comprises a projection on one of said members and aslot defined by axially sloping surface means disposed on the other ofsaid members, and said projection is cooperable with said axiallysloping surface means to cause said hammer member to acceleraterotatably with respect to said drive member in response to admission ofpressure fluid to said expansible chamber.

9. The invention set forth in claim 8 wherein:

said drive coupling includes axially sloping surface means cooperablewith said projection for reversible operation of said hammer member toimpact said anvil.

References Cited UNITED STATES PATENTS 3,001,429 9/1961 Sindelarl73---93.6 3,070,201 12/1962 Spyrldakis 173-936 3,128,400 4/1964Horuschuch et al. l7393.6 3,198,303 8/1965 Brown 173-93 3,389,756 6/1968Kawamoto 173-93.5

JAMES A. LEPPINK, Primary Examiner US. Cl. X.R. 173--105

